Blowback-type firing unit

ABSTRACT

A self-contained blowback-type firing unit insertable as a discrete subassembly in a gun body is disclosed. The subassembly may further comprise a barrel comprising a forward muzzle, a rearward open breech and a rearward spring abutment, a compression spring parallel to the barrel with a rearward end portion abutting the rearward spring abutment, and a bolt parallel to the spring and barrel, where the bolt comprises a firing pin that is moveable independently of the bolt.

FIELD

The present disclosure relates generally to firearms and, more specifically, to blowback-type automatic and semi-automatic firearms.

BACKGROUND

Blowback-type automatic and semi-automatic firearms have a common principle of operation which simply stated is this: a bolt reciprocates with respect to a barrel affixed to a body of the weapon to carry successive cartridges from a magazine into a rearward open breech of the barrel in position to be fired by a firing pin on the bolt. The explosive force of the fired cartridge propels the bolt rearwardly against the force of one or more compression springs. In a semi-automatic firing mode the bolt is caught by detent means in its rearward position and is moved forwardly by the spring for the next firing cycle only by operation of a trigger. In an automatic firing mode the bolt is propelled forwardly by the spring for repeated reciprocation and firing so long as the trigger is depressed.

Representative blowback-type automatic and semi-automatic firearms include the Beretta, the Uzi (see U.S. Pat. No. 4,335,643) and the Mendoza (see U.S. Pat. No. 3,906,833). Other blowback-type firearms include those shown in U.S. Pat. Nos. 4,019,423 and 2,437,548. In these prior designs the bolt reciprocates back-and-forth in sliding engagement with a cylindrical interior surface of the gun body. It is generally the practice in these conventional designs to add the bolt, barrel and spring one-by-one to the gun assembly as all of the parts are put together, not necessarily in immediate sequence and not as a separate independent subassembly. Field assembly and disassembly is relatively complicated. Foreign matter making its way to the slideable interface between the bolt and gun body can seriously impair the operation of the weapon, and cleaning is both necessarily frequent and painstaking.

The compression spring in most of the prior blowback-type firearms is aligned axially rearwardly of the barrel and bolt and relies upon a cap at the end of the gun body to provide a spring abutment in opposition to the bolt. The weapon disclosed in U.S. Pat. No. 3,906,833 is an exception to this but the other prior art designs mentioned above include the rearward spring contained by the gun body. This appreciably lengthens the weapon and increases its weight.

U.S. Pat. No. 4,327,626 discloses to some extent a combination of barrel-spring-bolt which is assembled together and then assembled within the remainder of the gun, though without carrying that concept to its highest advantage. That patent described a barrel having a rearward spring abutment and securing means for affixing the barrel to the gun body. A compression spring parallel to the barrel has a rearward end abutting the rearward spring abutment. Parallel to the spring and barrel is a reciprocable bolt having a forward spring abutment against which the forward end of the spring abuts and a firing pin base axially rearwardly of the barrel with apertures defined between the forward spring abutment and the base permitting entry and ejection of successive cartridges relative to the barrel breech. The bolt and barrel are in longitudinal slideable engagement.

A disadvantage of prior weapons with a rearward spring is that such a design shifts the center of gravity of the weapon rearwardly thus increasing the tendency of the barrel to buck upwardly in an uncontrolled fashion during recoil.

U.S. Pat. No. 4,649,800, the disclosure of which is incorporated herein by reference, discloses a self-contained blowback-type firing unit, the barrel-spring-bolt subassembly of which is able to be inserted as a discrete unit in and of itself in a gun body. Although U.S. Pat. No. 4,649,800 requires few internal mechanics, the design has a slow lock time (the time elapsed from the bolt release to discharge) of the weapon. More importantly, the long travel of the bolt creates a downward thrust of the weapon due to the weight of the bolt, making at least the first shot inaccurate.

While the prior devices are useful to a degree, they still suffer from certain drawbacks, including limitations on accuracy particularly during a fully automatic mode. Therefore, there exists a need in the art for an improved firearm that solves some or all of these problems, and does so in an efficient, reliable, low cost way.

SUMMARY

The present disclosure provides an improvement in a self-contained blowback-type firing unit insertable as a discrete subassembly in a gun body. The firing unit may include a barrel with a forward muzzle and a rearward open breech and a rearward spring abutment and securing means for affixing the barrel to the gun body. The firing unit also may include a compression spring parallel to the barrel with a rearward end abutting the rearward spring abutment. Also, the firing unit may include a reciprocable bolt parallel to the spring and barrel having a forward spring abutment against which the forward end of the spring abuts and a firing pin base axially rearwardly of the barrel with apertures defined between the forward spring abutment and the base permitting entry and ejection of successive cartridges relative to the barrel breech. The bolt and barrel may be in longitudinal slideable engagement. The bolt may comprise a firing pin that is moveable independently of the bolt.

In one form, a self-contained blowback-type firing unit insertable as a discrete subassembly in a gun body, comprises a barrel comprising a forward muzzle and a rearward open breech and a rearward spring abutment; a compression spring parallel to the barrel with a rearward end portion abutting the rearward spring abutment; a bolt parallel to the spring and barrel, where the bolt comprises a firing pin that is moveable independently of the bolt; and wherein the blowback-type firing unit insertable as a discrete subassembly in a gun body is self-contained.

In one embodiment, the firing pin may be located in a counter bore of the bolt. The firing pin may be retractable. In some embodiments the firing pin may be spring loaded. The bolt may further comprise a pin retainer. In other embodiments the bolt further comprises a firing pin anvil. The subassembly may comprise a barrel, a bolt, and a compression spring, where the subassembly may be completely removed from the gun body without disassembling the member parts of the subassembly.

In a preferred embodiment, the bolt can move forward against the barrel without discharge of the firing unit. The bolt and barrel may further be in longitudinal slideable engagement. The bolt may comprise a forward spring abutment against which a forward end portion of the spring abuts and a firing pin base axially rearwardly of the barrel with apertures defined between the forward spring abutment and the firing pin base permit entry and ejection of successive cartridges relative to the barrel breech. The barrel may be inserted laterally into the bolt, the compression spring may be telescoped around the barrel so that the rearward end of the compression spring is abutted by a rearward spring abutment on the barrel. The firing unit may further comprise a quick connection of a forward annular element by means of a bayonet attachment.

In one form, a self-contained blowback-type firing unit is insertable as a discrete subassembly in a gun body, which includes a barrel with a forward muzzle and a rearward open breech and a rearward spring abutment, and which includes a compression spring parallel to the barrel with a rearward end portion abutting the rearward spring abutment, and which further includes a reciprocable bolt parallel to the spring and barrel, the bolt comprising a forward spring abutment against which a forward end portion of the spring abuts, the bolt and barrel being in longitudinal slideable engagement, the improvement which comprises where a firing pin is movable within the bolt.

In one form, a firearm is disclosed, comprising a self-contained blowback-type firing unit insertable as a discrete subassembly in a gun body, a barrel comprising a forward muzzle and a rearward open breech and a rearward spring abutment; a compression spring parallel to the barrel with a rearward end portion abutting the rearward spring abutment; a bolt parallel to the spring and barrel, where the bolt comprises a bore containing a spring loaded firing pin.

In one embodiment, the firing unit further comprises matching slideably engaged longitudinal track surfaces on the barrel and bolt respectively which are other than cylindrical and circumferentially complete and which prevent rotation of the bolt on the barrel, the bolt being free of slideable engagement with any surface other than the barrel track surfaces. In one form of the firing unit the securing means on the barrel is the only support for the firing unit. The securing means may be forwardly on the barrel adjacent the muzzle and the firing unit may be cantilevered rearwardly therefrom. The apertures in the firing unit may be longitudinal slot means formed in the bolt with opposed sides defining opposed track surfaces, and radially extending tongue means are formed on the barrel with opposed sides defining opposed barrel track surfaces, the slot means having a length sufficient to permit lateral entry of the barrel into the bolt during assembly. The tongue means may be formed adjacent the breech of the barrel remote from the muzzle.

Another advantage of the present disclosure is that the firing unit is interchangeable within various gun bodies since it may be held in place only at its forward muzzle end in one form. Different firing units of varying caliber can also be inserted into a given style of gun body for a quick change in fire power.

Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description, including disclosed embodiments and drawings, are merely exemplary in nature intended for purposes of illustration only and are not intended to limit the scope of the present disclosure, its application or use. Thus, variations that do not depart from the gist of the present disclosure are intended to be within the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exploded elevation of a firing unit along with but removed from the remaining parts of a gun body in accordance with the principles of existing designs.

FIG. 2 illustrates an exploded view of the parts of a firing unit itself showing the barrel-spring-bolt disassembled in accordance with the principles of existing designs.

FIGS. 3 to 6 illustrate longitudinal sections taken along the centerline of a firing unit showing the bolt in various stages of reciprocation with respect to successive cartridges in accordance with the principles of existing designs.

FIG. 7 illustrates an enlarged transverse section taken along the line 7-7 of FIG. 3 in accordance with the principles of existing designs.

FIG. 8 illustrates a longitudinal section taken along the centerline of a firing unit showing the bolt of an open bolt configuration in accordance with the principles of existing designs.

FIG. 9 illustrates a longitudinal section taken along the centerline of a firing unit showing the bolt of a closed bolt configuration of another preferred embodiment of the present disclosure.

DETAILED DESCRIPTION

Referring first to FIG. 1, a gun body 10 is shown exploded in a disassembled state to include a cylindrical housing 11 having an open forward end 12 and an open rearward end 13. The open end 12 of the housing receives an annular forward cap 14 and the rearward end of the housing 13 receives a rearward cap 15. Both the forward and rearward caps 14 and 15 are detachable in a manner described hereinafter. A rearward portion 16 of the housing 11 has a length sufficient to enclose the reciprocable firing unit parts described below.

A forward end 17 of the housing 11 has attached to its underside a palm-held stock 18. Rearward of that is conventional cartridge magazine-receiving means 19. To the rear of the magazine-receiving means 19 is a conventional trigger 20 which cooperates through a suitable linkage (not shown) with a conventional sear 21 which is schematically suggested in each of FIGS. 3 to 6. To the rear of the trigger 20 is a pistol-type handle 22. The gun body 10 also may include conventional accompanying components such as a safety 23, a firing mode selector switch 24, a fore site 25 and a rear site 26. In addition a manual cocking element 27 is provided on the exterior of the rear portion 16 of the housing 11 of the gun body, operable in a slot 28 in the housing, to function in a manner described below. A bayonet indent 29 may also be included in the rear portion 16 of the housing 11 for the rearward cap 15.

The gun body 11 with all of its attendant parts referred to above, in combination with a firing unit 30 described below and with a typical loaded magazine in place in the magazine-receiving means 19, has a center of gravity well forward of the trigger 20 and its accompanying sear 21. An advantage of the forward center of gravity is that it creates a downward turning moment around the shooter's hand grasping the pistol handle 22 and this moment offsets at least some of the upward turning moment generated by recoil during firing. The result is that the weapon may be intentionally front-heavy and has less tendency to buck upwardly in the shooter's hand under the effect of recoil.

In addition, the accuracy of the weapon may be enhanced by the forward palm-held stock 18. Cradling of the front portion of the weapon with an upward palm (for example, the left hand of a right-handed shooter) in the manner of a shotgun is a more natural and easy manner of bringing the weapon quickly and accurately on target as compared to those automatic and semi-automatic weapons such as the Beretta which have a depending fist-held forward stock.

The firing unit 30 is indicated in FIG. 1 by a bracket and its principal parts are shown in an exploded view in FIG. 2. Three basic elements constitute the firing unit 30, namely a barrel 31, a compression spring 32 and a bolt 33. The barrel may include a forward muzzle portion 34 and a rearward open breech portion 35. A circular flanged rearward spring abutment 36 encircles the rearward breech portion 35 as shown particularly in FIG. 7.

The barrel also may include securing means for affixing it to the gun body, namely external threads 37 on the muzzle portion 34 and a shoulder 38 rearwardly thereof. A circular securing flange 39 (see FIGS. 3 to 6) may be provided on the inside of the forward portion 17 of the housing 11 of the gun body 10, and the forward cap 14 of the gun body may include an internally threaded annulus. The firing unit may be telescopically inserted into the housing 11 through the rearward open end 13 thereof so that the barrel muzzle 34 projects forwardly from the housing 11. The forward cap 14 is screwed by means of its internal threaded annulus onto the threads 37 on the barrel to hold the flange 39 of the housing 11 against the shoulder 38. In one embodiment, this form of securing means constitutes the only support for the firing unit 30 within the gun body 11 and the unit is therefore cantilevered rearwardly from that point of support.

An upper radially extending tongue 40 extends from the breech portion 35 of the barrel and a downwardly extending tongue 41 extends from the breech portion in the opposite direction. In the embodiment shown in FIG. 7, the upwardly extending tongue 40 is narrower than the downwardly extending tongue 41 and may include a relatively small arcuate indented surface 42 coaxial with the barrel axis. As shown in FIGS. 3 to 6 the downwardly extending tongue 41 defines a ramp 43 which guides successive cartridges into the barrel breech as described hereinafter.

The compression spring 32 is disposed concentric with and around the barrel 31 as shown in FIGS. 3 to 6 with a rearward end 44 abutting the rearward spring abutment 36 on the barrel.

The reciprocable bolt 33 comprises a plurality of parts, the principal ones being shown in FIG. 2 and also in FIGS. 3 to 6. In its final assembly the bolt 33 is disposed concentric with and around the spring 32 and barrel 31. A separate annular element 46 is fitted onto the forward end of the bolt 33 and may include a bayonet pin 47 which enters a bayonet slot 48 for quick release and connection. The annular element 46 defines a circular flanged forward spring abutment 49 against which a forward end 50 of the spring 32 abuts.

At the opposite end of the bolt 33 is a firing pin base 51 which is disposed axially rearwardly of the barrel 33 as seen in FIGS. 3 to 6. Two apertures in the form of slots extend longitudinally along the length of the bolt 33 between the forward spring abutment 49 and the firing pin base 51. There is an upper slot 53 and a lower slot 54, the latter being somewhat wider than the former and of sufficient length to allow for lateral insertion of the barrel.

The bolt 31 and barrel 33 are in longitudinal slideable engagement. Matching slideably engaged longitudinal track surfaces are provided on the barrel 31 and the bolt 33 which are other than cylindrical and circumferentially complete and which prevent rotation of the bolt on the barrel. The upper slot 53 and lower slot 54 on opposite sides of the bolt each have opposed sides defining opposed track surfaces. The upper tongue 40 and lower tongue 41 on the barrel each define opposed barrel track surfaces. These surfaces are in sliding engagement as seen in FIG. 7. In addition, the arcuate surface 42 of the upper tongue 40 of the barrel engages a small segment of the cylindrical interior of the bolt 31 as shown in FIG. 7 though this is not in any sense an encircling sliding surface.

The firing pin base 51 of the bolt 33 further may include conventional extractor means 57 appearing schematically in FIGS. 3 to 6 for pulling successive spent shells from the barrel breech. Firing pin means 58 in a central seat in the firing pin base are included to make firing contact with a cartridge when the bolt is reciprocated forwardly as described below. A draw-back element is provided in the firing pin base 51 in the form of an indented longitudinal slot 59 to cooperate with a corresponding land 60 on the manual cocking element 27 as described hereinafter. Detent means 61 are also included on the firing pin base to cooperate with the sear 21 in the conventional manner for cocking the bolt 33 against the force of the spring 32. As shown in FIG. 2 the detent 61 is part of a separate disc 62 which is removably secured by a bayonet connection to the rearward end portion of the bolt firing base 51. An axially disposed screw 63 passes through a center hole in the disc 62 to hold it in place, and at the same time locates the firing pin 58 within the central seat in the firing pin base 51.

A description of the assembly and operation of the device shown in FIGS. 1-7 may commence with the gun body 10 considered to be assembled as shown in FIG. 1 except for connection of the forward and rearward caps 14 and 15 and the cocking element 27. As to the firing unit 30, it is separately assembled by first inserting the firing pin 58 in the firing pin base 51 and attaching the disc 62 all by means of the screw 63. Next the barrel 31 is laterally inserted into the bolt 33 through the lower slot 54 and advanced in a forward axial direction so that its muzzle 34 projects from the front of the bolt and the tongues 40 and 41 fit within the slots 53 and 54. At that point the annular element 46 is not yet attached. Next the spring 32 is telescoped through the open forward end of the bolt 33 concentrically around the barrel 31 and within the bolt until the rearward end 44 of the spring contacts the rearward spring abutment 36. The annular element 46 is then pushed in a rearward direction into the remainder of the bolt so that its forward spring abutment 49 compresses the spring 33 at the forward end 50 thereof and a final turning motion of the annular element 46 causes the bayonet pin 47 to lock in the slot 48, thus assembling the firing unit in the state shown in FIGS. 1 and 5.

It will be recognized that this assembly of the firing unit is of the utmost simplicity. It involves simply lateral insertion of the barrel into the bolt, a telescoping of the spring around the barrel so that its rearward end is abutted by the rearward spring abutment on the barrel, and a quick connection of the forward annular element by means of the bayonet attachment to complete the assembly. The firing unit at that point is a discrete subassembly ready for insertion into the gun body.

The assembly of the firing unit 31 with the gun body 10 is done in four simple and quick steps. First the cocking element 27 is connected to the bolt by placing the land 60 in the corresponding slot 59 in the firing pin base 51. Next the firing unit is telescoped forwardly from the position shown in FIG. 1 into the open rearward end 13 of the housing 11 until the shoulder 38 on the barrel abuts the inward flange 39 of the housing. The third step is simply to screw the forward cap 14 about the threads 37 on the muzzle of the barrel until the barrel is affixed with respect to the gun body by compression of the housing flange 39 between the shoulder 38 and the forward cap 14. Finally the rearward cap 15 is slipped over the end 16 of the housing 11 and with a quick turn is secured in its bayonet indent 29. As the firing unit 30 is advanced into the housing 11 the cocking element 27 is guided into the slot 28 in the housing. The weapon is now fully assembled.

The movement of the parts of the firing unit during firing is shown sequentially in FIGS. 3 to 6. The cocking element 27 is pulled rearwardly by hand in the slot 28 of the housing 11 until the sear 21 catches the detent 61 as shown in FIG. 3. At that point the cocking element is advanced forwardly to its initial position and is released from the bolt. The weapon is then in a cocked position.

Upon squeezing of the trigger 20 the detent 61 is released from the position of FIG. 3. Meanwhile a cartridge 71 comprising a bullet 72 and shell 73 is advanced upwardly in a conventional manner from its spring-biased magazine through the lower slot 54. Release of the sear 21 from the detent 61 permits the spring 32 to advance the bolt 33 forwardly to the left as shown in all of the figures. At the point in its reciprocation shown in FIG. 4 the cartridge 71 is contacted by the firing pin base and advanced forwardly, guided by the ramp 43, into the breach portion of the barrel 31. When fully inserted in the breech as shown in FIG. 5 the firing pin 58 detonates the cartridge 71. At this point the bolt 33 is in its forwardmost position.

The explosive effect of the fired cartridge causes the bolt 33 to be propelled rearwardly as shown in FIG. 6 and as the bullet 72 exits from the muzzle of the weapon the extractor 57 pulls the spent shell 73 from the barrel breech and a conventional ejector (not shown) within the gun body displaces it outwardly through the upper slot 53 of the bolt.

If the weapon is on automatic firing mode, the sear 21 does not engage the detent 61 so long as the trigger 20 is squeezed and therefore the bolt 33 reciprocates back to its FIG. 3 position and immediately advances forward for another cycle. In the semi-automatic firing mode the sear 21 engages the detent 61 and only another squeezing of the trigger will cause the firing cycle to be repeated.

Throughout these stages of reciprocation of the parts of the firing unit, the barrel 31 and bolt 33 may be in slideable engagement with one another along the matching longitudinal track surfaces shown in FIG. 7. In some embodiments, these surfaces are not cylindrical and circumferentially complete and the bolt therefore does not encircle the barrel, though it does prevent rotation of the bolt on the barrel. It will be recognized that the bolt may be free of slideable engagement with any surface other than the barrel track surfaces. In some embodiments it slides only on the sides of the tongues 40 and 41 and the small arcuate surface 42. There may be ample clearance within the housing 11 to permit the bolt 33 to reciprocate back and forth telescopically within the housing 11 without in any way contacting the interior surfaces of the housing. The entire support of the firing unit throughout this firing sequence may be at its forward end where the muzzle is secured to the housing.

The two main designs used in auto loading weapons are open bolt and closed bolt types.

Open bolt weapons have a fixed firing pin located within the bolt body itself, with the bolt locked back under spring tension. Once released by a devise, the bolt travels forward within the body of the weapon pushing a cartridge from the magazine into the chamber of the barrel. The rapid forward motion of the bolt strikes the chambered cartridge causing discharge. The bolt also houses an extractor device. Upon discharge of the cartridge, gas blow back occurs, pushing the bolt back. The empty cartridge case is extracted and ejected from the open cartridge port in the housing. This action completes one full cycle of the weapon.

Closed bolt weapons have non-fixed (retractable) firing pins located within the bolt body. With the bolt locked back under spring tension, that once released by a device, travels forward within the body of the weapon, pushing a cartridge from the magazine into the chamber of the barrel. However, the weapon does not yet discharge as it does with an open bolt fixed firing pin design. Located below the bolt, within the frame of the weapon is a hammer, hammer spring, sear, sear spring and trigger. The hammer is under spring tension and is released by pulling the trigger. The hammer then travels forward and strikes the retracted firing pin. The firing pin then strikes the chambered cartridge causing discharge. Finally, the same gas release blow back action takes place as described in the open bolt operation above.

FIG. 8 illustrates a longitudinal section taken along the centerline of a firing unit showing the bolt of an open bolt configuration in accordance with the principles of existing designs. Referring to FIG. 8, the firing unit 830 is shown to include a tubular housing 811 having a barrel 831 and bolt 833. The forward end of the tubular housing 811 has a barrel retainer 814 and the rearward end of the housing 811 has a bolt hold open cap 815. In its final assembly, the bolt 833 may be disposed concentric with and around the spring 832 and barrel 831. The bolt 833 may comprise a fixed firing pin 858 which is disposed axially rearwardly of the barrel 833 as seen in FIG. 8. In some embodiments, the bolt 831 and barrel 833 may be in longitudinal slideable engagement. The spring 832 may be telescoped through the forward end of the bolt 833 concentrically around the barrel 831 and within the bolt until the rearward end of the spring contacts the barrel flange 836. In the embodiment of FIG. 8, the bolt moves forward against the fixed barrel with discharge of the firearm.

The bolt 833 may further include conventional extractor means appearing schematically in FIGS. 3 to 6 for pulling successive spent shells from the barrel breech. Fixed firing pin 858 is included to make firing contact with a cartridge when the bolt is reciprocated forwardly. A draw-back element may be provided in the firing pin base in the form of an indented longitudinal slot to cooperate with a corresponding land on a manual cocking element. Detent means may also be included on the firing pin base to cooperate with the sear in the conventional manner for cocking the bolt 833 against the force of the spring 832.

FIG. 9 illustrates a longitudinal section taken along the centerline of a firing unit showing the bolt of a closed bolt configuration of another preferred embodiment of the present disclosure. Referring to FIG. 9, the firing unit 930 is shown to include a tubular housing 911 having a barrel 931 and bolt 933. The rearward end of the housing 911 has a bolt hold open cap 915. The bolt 933 may comprise a firing pin spring 957, a spring loaded firing pin 958, a firing pin anvil 959, and a counter bore 960. In the embodiment of FIG. 9, the bolt moves forward against the fixed barrel without discharge of the firearm. The firing unit 930 is modified by counter-boarding the firing pin canal, so that it will accept a non-fixed (retractable) firing pin that is spring loaded with a pin retainer. In some embodiments, a hammer (not shown) is released by the pull of the trigger, where the hammer then contacts the spring loaded firing pin 958 to discharge the gun. In a preferred embodiment, the modification of the bolt to be able to receive non-fixed firing pin converts the firing unit from an open bolt to a closed bolt type. In a preferred embodiment, the firing unit begins operation as a closed bolt design for the first round to be fired, as the bolt is in a closed position, as seen in FIG. 9. In some embodiments, where the firing unit begins operation as a closed bolt design for the first round to be fired, the action of the bolt then proceeds in a manner similar to an open bolt configuration, in that when the bolt moves forward to the closed position, the firing pin of the bolt contacts the shell, discharging the gun, even though the spring is not fixed. In a preferred embodiment, the blowback-type firing unit insertable as a discrete subassembly in a gun body may be self-contained in that the subassembly, where the subassembly comprises a barrel, a bolt, and a compression spring, where the subassembly may be completely removed from the gun body without the need to disassemble the member parts of the subassembly.

In a preferred embodiment, the barrel 931, spring 32, and bolt 933 are not fixedly attached to the firing unit. For example, the barrel 931 may not be screwed into the frame of the gun body 10. In some embodiments, the barrel may rest against a structure, such as a barrel flange 836 or barrel retainer 814, to prevent movement of the barrel 931 within the firing unit, while allowing the firing unit to be easily removed from the gun body, and allowing for easy disassembly of the firing unit. In some embodiments, the barrel will be kept from rotating. The upper slot 53 and lower slot 54 on opposite sides of the bolt each may have opposed sides defining opposed track surfaces. The upper tongue 40 and lower tongue 41 on the barrel each may define opposed barrel track surfaces. These surfaces may be in sliding engagement, with matching slideably engaged longitudinal track surfaces on the barrel and bolt respectively defined by radially extending tongue means on one of the barrel and bolt and slot means on the other of the barrel and bolt and which prevent rotation of the bolt on the barrel. The arcuate surface 42 of the upper tongue 40 of the barrel may engage a small segment of the cylindrical interior of the bolt 31 as shown in FIG. 7 though this is not in any sense an encircling sliding surface.

One advantage of an embodiment as shown in FIG. 9 is that the bolt begins the firing process from a closed position, so the bolt does not need to travel within the body of the weapon, which allows increased accuracy of at least the first shot of the weapon. In some embodiments, the reciprocating action of the bolt in the barrel after the initial fired shot may help to create balance and contribute to the accuracy of the weapon, particularly in full auto mode.

The advantages of this closed bolt configuration include a much more accurate first shot capability, a much faster lock time (where time is elapsed from the trigger pull to discharge), a decreased chance for dirt and foreign matter to enter the weapon, a much quieter mechanical function, and allowing for weapon suppression for covert use (since open bolt weapons have difficulty in being suppressed). Shells of any caliber used in law enforcement or military applications may be used in this firing unit including, but not limited to shells within the range of 0.22 LR (Long Rifle) to 0.45 ACP (Automatic Colt Pistol) caliber. In particular, 9 mm, 10 mm, 40 S&W (Smith & Wesson), or 45 ACP calibers are preferred.

The scope of the present disclosure is set forth in the following claims and is not limited to the specific preferred embodiment described above. 

What is claimed is:
 1. A blowback-type firing unit insertable as a discrete subassembly in a gun body, comprising a barrel comprising a forward muzzle and a rearward open breech and a rearward spring abutment; a compression spring parallel to the barrel with a rearward end portion abutting the rearward spring abutment; and a bolt parallel to the spring and barrel, where the bolt comprises a firing pin that is moveable independently of the bolt; wherein the blowback-type firing unit insertable as a discrete subassembly in the gun body is self-contained.
 2. A firing unit according to claim 1, wherein the firing pin is located in a counter bore of the bolt.
 3. A firing unit according to claim 1, wherein the firing pin is retractable.
 4. A firing unit according to claim 1, wherein the firing pin is spring loaded.
 5. A firing unit according to claim 1, wherein the bolt further comprises a firing pin anvil.
 6. A firing unit according to claim 1, wherein the subassembly comprises a barrel, a bolt, and a compression spring, where the subassembly may be completely removed from the gun body without disassembling the member parts of the subassembly.
 7. A firing unit according to claim 1, wherein the bolt can move forward against the barrel without discharge of the firing unit.
 8. A firing unit according to claim 1, wherein the bolt and barrel are in longitudinal slideable engagement.
 9. A firing unit according to claim 1, wherein the bolt comprises a forward spring abutment against which a forward end portion of the spring abuts and a firing pin base axially rearwardly of the barrel with apertures defined between the forward spring abutment and the firing pin base permit entry and ejection of successive cartridges relative to the barrel breech.
 10. A firing unit according to claim 1, wherein the barrel is inserted laterally into the bolt, the compression spring is telescoped around the barrel so that the rearward end of the compression spring is abutted by a rearward spring abutment on the barrel.
 11. A firing unit according to claim 1, further comprising a quick connection of a forward annular element by means of a bayonet attachment.
 12. In a self-contained blowback-type firing unit insertable as a discrete subassembly in a gun body, which includes a barrel with a forward muzzle and a rearward open breech and a rearward spring abutment, and which includes a compression spring parallel to the barrel with a rearward end portion abutting the rearward spring abutment, and which further includes a reciprocable bolt parallel to the spring and barrel, the bolt comprising a forward spring abutment against which a forward end portion of the spring abuts, the bolt and barrel being in longitudinal slideable engagement, the improvement which comprises where a firing pin is movable within the bolt.
 13. A firing unit according to claim 12, wherein the bolt can accept a non-fixed firing pin.
 14. A firing unit according to claim 12, wherein the bolt is spring loaded with a pin retainer.
 15. A firing unit according to claim 12, wherein the bolt further comprises a retractable firing pin.
 16. A firing unit according to claim 12, wherein the firing pin is spring loaded.
 17. A firing unit according to claim 12, wherein the bolt further comprises a firing pin anvil.
 18. A firing unit according to claim 12, wherein the bolt can move forward against the barrel without discharge of the firing unit.
 19. A firing unit according to claim 12, further comprising matching slideably engaged longitudinal track surfaces on the barrel and bolt respectively defined by radially extending tongue means on one of the barrel and bolt and slot means on the other of the barrel and bolt and which prevent rotation of the bolt on the barrel, the barrel track surfaces being limited to a location rearwardly of the rearward end portion of the spring.
 20. A firearm, comprising: a self-contained blowback-type firing unit insertable as a discrete subassembly in a gun body, comprising: a barrel comprising a forward muzzle and a rearward open breech and a rearward spring abutment; a compression spring parallel to the barrel with a rearward end portion abutting the rearward spring abutment; and a bolt parallel to the spring and barrel, where the bolt comprises a bore containing a spring loaded firing pin. 